Dear Sadid, I agree with you that my implementation is completely stupid and a waste of time in real life and that's why I don't like the current evaluation metric of Cody. A (time and/or memory)-based evaluation would be much more interesting. With the current evaluation metric, Cody promotes hacking and cracking (which is also fine), but players don't learn good manners for developing efficient code.

@Mechatrobrnotronik: I tested your code.
function ans = test_fkt(A,n)
A(:,n) = ''
end
Works for me. Returning A with removed column n.
Nonetheless I am interested in what '' actually does. I couldn't find it in the command reference.

For those who wonder how such low scores are being reported in Cody, it is because many players are changing the actual function call. The result is obvious to those of us who have solved many of these challenges.